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A recently developed infrared (IR) local heating method is fairly effective to reduce springback of advanced high strength steel in manufacturing processes of car chassis. Although parabolic heaters, consisting of an IR lamp located on the focus of a parabolic reflector, can reduce springback in stamping processes, non-negligible temperature changes are generated in the heated area. For this reason, an improved heater has been required for the IR heating method. In this work, an overlapping heater array is designed to solve the problem of the parabolic heater for the IR local heating method. The overlapping heater array can reduce the temperature change in the heated area. In the overlapping heater array, the parabolic heaters are connected in series. The connected parabolic heaters are then placed on both sides of a thin sheet metal and intersected to reduce the temperature change. In order to design a more efficient overlapping heater array, a simple design parameter was employed. The numerical and experimental verifications have shown that the overlapping heater array drastically reduces the temperature change in the heated area. [ABSTRACT FROM AUTHOR]

The boiler equipment should be able to adapt to the load requirements and overcome the interference of various external conditions. By establishing a one-dimensional single-channel general numerical calculation model suitable for flow instability analysis of ultra-supercritical boilers at 700 °C, the rules of flow in the tubes are calculated. The 7th loop and the 22nd loop of the boiler water wall are selected as typical loops, and the dynamic characteristics of the two loops are calculated. The results show that after applying different multiples of heat flux disturbance, regardless of whether metal heat storage is considered, the inlet and outlet mass flow rates of the two circuits show inverse dynamic responses and eventually return to a steady state. When considering heat storage, it takes about 63 s for the 7th loop to return to stability. The recovery and stabilization time of the 22nd loop is about 60 s. Metal thermal storage has a positive effect on the settling time of the pipe section after heat flux disturbance. And when the maximum heat flux disturbance is applied, the maximum wall temperatures of the two loops are 443.9 °C and 446.5 °C, and the boiler can operate safely and stably. [ABSTRACT FROM AUTHOR]

A numerical study is conducted to investigate heat transfer characteristics of supercritical water flowing upward in an inclined smooth tube under uniform heating conditions. In this study, model verification was performed under the conditions of low heat flux and high heat flux to ensure the accuracy of experimental data. Inner wall temperature and heat flux distribute non-uniformly on the circumference due to the influence of natural convection. The increase of heat flux enhances the non-uniform circumferential distribution, while the increase of mass flux reduces the non-uniform circumferential distribution. Heat transfer of upward vertical and inclined flows is compared under low and high heat flux conditions. Radial distributions of fluid temperature, density, specific heat capacity, velocity, and turbulent kinetic energy are presented and analyzed. The analysis shows that the increase of heat flux reduces radial turbulence and heat-absorbing capacity of the boundary fluid, while increases radial temperature and density gradient. Three dimensionless buoyancy parameters are used to evaluate the buoyancy effect of inclined flow. [ABSTRACT FROM AUTHOR]